<!DOCTYPE html>
<html>
<head>
    <title>setInterval() test</title>
    <script>
        document.addEventListener("DOMContentLoaded", function () {
            var output = document.getElementById("output");
            var counter = 0;
            function updateOutput () {
                output.innerHTML = `setInterval() was called ${counter} times!`;
            }
            updateOutput();
            setInterval(function () {
                counter++;
                updateOutput();
            }, 1000);
        });
    </script>
</head>
<body>
    <div id="output"></div>
</body>
</html>
